1. Field of the Invention
The present invention relates to a speed change transmission apparatus, and more particularly to a speed change transmission apparatus including a planetary transmission device for, by a plurality of planetary transmission mechanisms, combining an output from a stepless speed change device and the engine drive not subject to a speed change by the stepless speed change device, or combining an output from an electric motor and the engine drive.
2. Description of Related Art
When the above speed change transmission apparatus includes a stepless speed change device, the speed of the stepless speed change device is changed and the speed range setting device is duly switched in conjunction with the change in speed, so that the drive outputted from the engine and stepless speed change device and combined is divided into a plurality of speed ranges and is outputted steplessly at each of the speed ranges. When the above speed change transmission apparatus includes an electric motor, on the other hand, the speed of the electric motor is changed and the speed range setting device is duly switched in conjunction with the change in speed, so that the drive outputted from the engine and electric motor and combined is divided into a plurality of speed ranges and is outputted steplessly at each of the speed ranges.
This type of speed change transmission apparatus was previously developed and disclosed in JP 2007-091139 A. The structure disclosed in JP 2007-091139 A will be described hereunder, but the purpose is to compare the structure disclosed in JP 2007-091139 A and the structure in the present application in order to describe the present application, not necessarily to acknowledge the structure disclosed in JP 2007-091139 A as prior art. FIG. 13 is a line drawing of a travel transmission apparatus for a tractor mounting the previously developed speed change transmission apparatus. As illustrated, the previously developed speed change transmission apparatus includes a stepless speed change device 20, a planetary transmission device P, a speed range setting device C, an auxiliary speed change device K and forward-reverse changeover device B.
The planetary transmission device P includes a first planetary transmission mechanism P1, a second planetary transmission mechanism P2 and a third planetary transmission mechanism P3. The first planetary transmission mechanism P1 includes a ring gear receiving the engine drive not subject to the speed changing action of the stepless speed change device 20, and a sun gear receiving the output from the stepless speed change device 20. The second planetary transmission mechanism P2 includes a carrier interlocked with the ring gear of the first planetary transmission mechanism P1, and a ring gear interlocked with the carrier of the first planetary transmission mechanism P1. The third planetary transmission mechanism P3 includes a sun gear interlocked with the sun gear of the second planetary transmission mechanism P2, and a carrier interlocked with the ring gear of the second planetary transmission mechanism P2. The speed range setting device C includes a first clutch C1 and a second clutch C2. The forward-reverse changeover device B includes a forward clutch CF and a reverse clutch CR.
In FIG. 13, numeral 3 denotes a rear wheel differential mechanism, and numeral 7 denotes a front wheel differential mechanism.
FIG. 15 illustrates a relationship between speed change states of the stepless speed change device 20, speed ranges and output speeds of the output shaft 80 (referred to hereinafter as output speed) in the previously developed speed change transmission apparatus. In FIG. 15, “−MAX” indicates the speed change state of the maximum speed when the stepless speed change device 20 is in the speed change area on the reverse rotational output side, “0” indicates when the stepless speed change device 20 is in neutral, and “+MAX” indicates the speed change state of the maximum speed when the stepless speed change device 20 is in the speed change area on the forward rotational output side.
FIG. 16 is a diagram showing a relationship between the speed ranges and clutching states in the previously developed speed change transmission apparatus. In FIG. 16, “engaged” indicates that the clutches C1, C2, CL and CH are engaged, while “−” indicates that the clutches C1, C2, CL and CH are not engaged.
FIG. 14 is a block diagram of the speed change apparatus of the previously developed speed change transmission apparatus. This speed change apparatus includes a speed change lever 100, a speed change mode selection device 102 and a control device 105. The control device 105 switches the first clutch C1 and second clutch C2 and changes the speed of the stepless speed change device 20 based on the data detected by a speed change command detection device 101 connected to the speed change lever 100. The control device 105 switches the low speed clutch CL and high speed clutch CH based on commands from the speed change mode selecting device 102.
As illustrated, the previously developed speed change transmission apparatus is as follows.
That is, when the first clutch C1 of the speed range setting device C is engaged and the second clutch C2 is not engaged while the low speed clutch CL of the auxiliary speed change device K is engaged, and the stepless speed change device 20 is changed from “−MAX” to “+MAX” in that state, the output shaft 80 is operated in the first speed range in low speed mode, and the output speed accelerates steplessly from “0”. Changing the stepless speed change device 20 to “+MAX” results in an output speed “Vlm.” When the first clutch C1 is then switched to a disengaged state and the second clutch C2 is switched to an engaged state, and the stepless speed change device 20 is changed from “+MAX” to “−MAX” in this state, the output shaft 80 is driven at the second speed range in low speed mode, and the output speed accelerates steplessly from “Vlm”. Changing the stepless speed change device 20 to “−MAX” results in an output speed of “Vlh.”
When the high speed clutch CH of the auxiliary speed change device K is engaged and the second clutch C2 is disengaged while the first clutch C1 of the speed range setting device C is in an engaged sate, and the stepless speed change device 20 is changed from “−MAX” to “+MAX” in that state, the output shaft 80 is driven at the first speed range in high speed mode, and the output speed accelerates from “0” steplessly. Changing the stepless speed change device 20 to “+MAX” results in an output speed of “Vhm.” When the first clutch C1 is then disengaged and the second clutch C2 is engaged, and the stepless speed change device 20 is changed from “+MAX” to “−MAX” in this state, the output shaft 80 is driven at the second speed range in high speed mode, and the output speed accelerates from “Vhm” steplessly. Changing the stepless speed change device 20 to “−MAX” results in an output speed of “Vhh.”
When the previously developed speed change transmission apparatus is mounted on a traveling device of a tractor, the output from the speed range setting device C can undergo auxiliary speed changes and be transmitted to the output shaft 80 acting as an output rotator, so as to allow the traveling device to be driven and speed-changed steplessly at high torque while working, and to allow the traveling device to be driven at continuously variable speed at high speed when moving. The output from the speed range setting device C can also be converted to forward drive and reverse drive and be transmitted to the output shaft 80, making it possible to travel by easily switching between forward and reverse movement.
The previously developed speed change transmission apparatus tends to be economically disadvantageous in attempting to diversify tractor design to meet demand.
That is, in addition to demand requiring the ability to switch between low and high speed modes, there is also demand with no such need for switching between low and high speed modes. Tractor models, whichever they do and do not allow switching between low and high speed modes, include forward-reverse changeover devices. Diversification on the basis of the previously developed speed change transmission apparatus results in manufacturing models in which some has an output side of the speed range setting device C and an input side of the forward-reverse changeover device B interlocked by means of the auxiliary speed change device K and some interlocked not means of the auxiliary speed change device K.